The invention relates to a disc brake for a commercial vehicle.
Such disc brakes, also referred to as sliding caliper disc brakes, are well known. The brake pads here, each comprising a pad-carrier plate and a friction lining retained thereon, are pushed in the direction of the brake-disc axis into the pad slots of the brake carrier, which is retained at a fixed location on the vehicle.
During braking, when the brake pads are pressed against the brake disc, the friction fit between the friction lining of the respective brake pad and the brake disc gives rise to the brake pad being subjected, in the direction of rotation of the brake disc, to a torque which is absorbed by the exit-side brake carrier lug.
However, over the course of operation of the brake pads, this results in so-called tangential diagonal wear to the brake pads such that, as seen in the main braking direction, i.e. when the commercial vehicle is travelling forwards, said brake pads wear to a more pronounced extent on the entry side than on the exit side.
It is therefore necessary for the brake pads, as soon as they reached their wear limit in the regions which are worn to a relatively pronounced extent, to be changed over, there still being usable wear volume available in the remaining regions of the brake pad or of the friction linings.
Of course, this stands in the way of operational-cost optimization, which is a constant aim, in particular also because commercial vehicles are usually equipped with a multiplicity of disc brakes, each having the aforementioned problems.
Although the prior art discloses disc brakes of which the brake pads have form-fitting elements which engage in a corresponding manner in the respective brake carrier, the form fits produced thereby are not suitable for preventing the problem of diagonal wear. In particular, the brake pads are not retained in a form-fitting manner in both directions of rotation of the brake disc.
DE 21 38 776 A discloses a disc brake in which the brake pads are mounted in guide grooves of the brake carrier by way of laterally formed protrusions, wherein, during braking, the entry-side protrusion is supported radially on the upper wall of the guide grooves without the brake carrier being capable of effectively absorbing a torque in this region. A comparable design is dealt with in DE 22 55 678 A.
It is an object of the invention to develop a disc brake of the type in question such that the service life of the brake pads and the operational costs are lowered.
The configuration of the disc brake according to the invention, in particular of the corresponding parts of the brake carrier, on the one hand, and of the brake pads, on the other hand, means that the torque which acts on the respective brake pad during braking acts on the entry-side region of the brake carrier, in particular on the entry-side brake carrier lug, and therefore the brake pad acts more or less as a tie.
As a result of the at least one form fit with the brake carrier, which according to the invention is provided on the entry side, the brake pad is more or less braced with the brake carrier in both directions of rotation of the brake disc. That is to say the torque acting on the brake pad is absorbed in the first instance exclusively by the entry-side region of the brake carrier, in particular, in this case, the brake carrier lug.
In the case of relatively large braking moments, which apply torque to the brake pads, it is possible for the entry-side brake carrier lug to flex to the extent where the brake pad, on the exit side abuts the associated brake carrier lug. It is always ensured, in the case of such torque absorption, that there is no diagonal wear to the brake pad.
The form fit between the brake pad and the brake carrier can be produced in different ways.
According to one idea of the invention, provision is made for the respective pad-carrier plate, on the side which is directed towards the floor of the brake carrier, to have a protrusion, which, as seen in the direction of rotation of the brake disc, butts against at least one supporting surface of the brake carrier, said supporting surface being formed by a protuberance arranged on the floor of the pad slot. It is also conceivable for the associated brake carrier lug to be used as a further supporting surface, and therefore the protrusion is positioned between the two supporting surfaces and butts against the same.
The two mutually opposite supporting surfaces, accommodating the associated protrusion of the brake pad between them, are arranged parallel to one another, are of smooth-surface design and run tangentially to the brake disc, and therefore the brake pad can be pushed in radially, as in relation to the brake disc.
According to the invention, it is indeed the case that the brake pad is supported on the brake carrier in both directions of rotation of the brake disc at least on the entry side, but it is preferred for the support to be provided both on the entry side and on the exit side, and therefore the brake pad may be of mirror-symmetrical design, as seen in relation to a radial centre axis. Depending on the direction of rotation of the brake disc, i.e. depending on whether travel is in the forward direction or in reverse, the entry side and exit side change round. That is to say the entry side for forward travel becomes the exit side for reverse travel, and vice versa.
Another variant of the invention makes provision for the support to be provided by a form fit between the brake pad and the brake carrier, for which purpose a claw-like formation is provided in that peripheral region of the pad-carrier plate which is directed towards the brake carrier lug, and said claw-like formation has an accommodating groove, into which is fitted a dimensionally adapted retaining pin of the brake carrier lug. This therefore also achieves the situation where the brake pad is arrested on the brake carrier lug in both directions of rotation of the brake disc.
Instead of a claw-like formation of the brake pad and a retaining pin of the brake carrier lug, it is also, of course, possible for the brake carrier lug to be of claw-like design and for the brake pad to be provided with a retaining pin, which engages in the groove formed in the brake carrier lug.
Otherwise, the form-fitting elements or formations of the brake pad are arranged on the brake carrier plate.
By virtue of the brake pad being more or less clamped in the direction of rotation of the brake disc both on the entry side and the on the exit side, it is possible for the corresponding brake pad to perform the function of a strut if one of the two pad slots is formed without a strut connecting the brake carrier lugs to one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.